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INDIANAPOLIS – Like a miniscule SWAT team, microscopic particles of a platinum-based chemotherapy drug could be deployed within a tumor to unleash a forceful three-pronged attack on cancer with minimal collateral damage to healthy tissue, suggests early research being presented at the 55th Annual Meeting of the American Association of Physicists in Medicine (AAPM).

The research shows these “nanoparticles” could be used during radiation treatment to increase damage to the tumor’s blood supply, as well as the cells that cause cancer to recur, while also delivering chemotherapy with fewer side effects.

The study builds on research showing that nanoparticles (100 million of which could fit on the head of a pin) made of precious metals such as platinum and gold can increase the dose and accuracy of radiation therapy. Another study being presented at AAPM suggests that shell-shaped hollow gold nanoparticles can enable the same cancer-killing benefits of standard radiation therapy at much lower doses than typically used.

Platinum nanoparticles

Currently, physicians routinely insert rice grain-sized implants into tumors to guide radiation therapy by marking the location of the cancer and, therefore, where the x-rays should be directed. Harvard Medical School and other researchers are developing their own “smart” implants by coating them with a polymer film containing nanoparticles of platinum-based cisplatin, which is one of the most commonly used chemotherapy drugs. Once the smart implant is placed inside the tumor, the nanoparticles could be released to attack the cancer by interrupting its blood supply, as well as damaging its DNA via chemotherapy and a highly targeted and enhanced dose of radiation.

“The nanoparticles could be programmed to deliver a sustainable one-two-three punch to the cancer where it hurts the tumor the most,” said Wilfred F. Ngwa, Ph.D., faculty in the department of radiation oncology at Brigham & Women’s Hospital, Dana Farber Cancer Institute and Harvard Medical School, Boston. “We anticipate this could provide huge benefits, including helping prevent cancer recurrence, and significantly increasing survival and quality of life for cancer patients.”

By using Food and Drug Administration (FDA)-approved concentrations of cisplatin nanoparticles released from the smart implant, researchers calculated that tumor blood vessels and high-risk cancer cells would receive about twice the radiation dose – and therefore, sustain more damage – as during standard radiation therapy. Putting theory into practice, the researchers currently are testing this nanoparticle-aided treatment in mice, which, if successful will lead to human trials.

“Based on the promising results, we believe that our new approach presents enormous possibilities for customizing and significantly improving radiation therapy,” said Dr. Ngwa. “If successfully developed, the new method could be employed at virtually no additional inconvenience to patients to enhance treatment of lung and prostate cancers, among others.”

Hollow gold nanoparticles

Researchers at UT Southwestern Medical Center, Dallas, studied the concept of injecting shell-shaped hollow gold nanoparticles directly into tumors to enhance the effects of radiation. While still microscopic, the hollow nanoparticles are about 10 times the size of standard solid nanoparticles.

When radiation treatment x-rays strike gold nanoparticles, they create an avalanche of electrons near the tumor cells, making the radiation more lethal to the cancer. Making the nanoparticles larger increases the amount of surface area and, therefore, their ability to boost radiation to kill tumor cells, said the researchers.

Using a clonogenic assay – a standard cancer research method to determine how a treatment affects cells – researchers found that hollow gold nanoparticles produced the same biological treatment effect at much lower doses of radiation.

“This preliminary research suggests gold nanoparticles can boost the cancer-killing power of the radiation so that much lower doses of radiation can be used to achieve the same effect,” said Weihua Mao, Ph.D., assistant professor in the Department of Radiation Oncology at UT Southwestern Medical Center. “It’s safer and better for the patient to be exposed to less radiation, so this therapy holds promise.”

In addition to Dr. Ngwa, co-authors of the study on platinum nanoparticles being presented at AAPM are Mike Makrigiorgos and Ross Berbeco, also from Harvard Medical School, and Yucel Altundal and Erno Sajo, from the University of Massachusetts at Lowell.

In addition to Dr. Mao, co-authors of the study on hollow gold nanoparticles being presented at AAPM are Chienwen Huang, Vasant Kearney, Kwang Song, Preston Christensen, Xiankai Sun and Timothy Solberg, also of UT Southwestern Medical Center, as well as Yaowu Hao of UT Arlington.

About Medical Physicists If you ever had a mammogram, ultrasound, X-ray, MRI, PET scan, or known someone treated for cancer, chances are reasonable that a medical physicist was working behind the scenes to make sure the imaging procedure was as effective as possible. Medical physicists help to develop new imaging techniques, improve existing ones, and assure the safety of radiation used in medical procedures in radiology, radiation oncology and nuclear medicine. They collaborate with radiation oncologists to design cancer treatment plans. They provide routine quality assurance and quality control on radiation equipment and procedures to ensure that cancer patients receive the prescribed dose of radiation to the correct location. They also contribute to the development of physics intensive therapeutic techniques, such as stereotactic radiosurgery and prostate seed implants for cancer to name a few. The annual meeting is a great resource, providing guidance to physicists to implement the latest and greatest technology in a community hospital close to you.

About AAPM
The American Association of Physicists in Medicine (www.aapm.org) is a scientific, educational, and professional organization with nearly 8,000 medical physicists. Headquarters are located at the American Center for Physics in College Park, Md.